Liquid crystal display device

ABSTRACT

A liquid crystal display device which can prevent the generation of bubbles on an adhesive surface between a liquid crystal display panel and a face plate which protects the liquid crystal display panel is provided. In mounting the face plate on an upper polarizer of the liquid crystal display panel by way of an adhesive material, a picture frame is formed on a periphery of the face plate for enhancing design property. Although the picture frame is formed by printing black ink, a quantity of Si present in the black ink is set to not more than 0.7% and not less than 0.01% thus preventing the generation of bubbles attributed to defective adhesion between the face plate and the adhesive material.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. Ser. No.12/358,428, filed Jan. 23, 2009, the contents of which are incorporatedherein by reference.

The disclosure of Japanese Patent Application No. 2008-15181 filed onJan. 25, 2008 including the specification, drawings and abstract isincorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid crystal display device, andmore particularly to a technique which can enhance a strength andvisibility of a miniaturized display device used in a mobile phone orthe like.

2. Description of Related Arts

With respect to a liquid crystal display device, there has been a strongdemand for making a profile size of the display device smaller whilemaintaining a screen at a fixed size as well as a demand for thereduction of a thickness of a liquid crystal display panel. To achievethe reduction of thickness of the liquid crystal display panel, athickness of the liquid crystal display panel is decreased by polishingan outer side of the liquid crystal display panel after manufacturingthe liquid crystal display panel.

With respect to a glass substrate which is used for forming a TFTsubstrate which constitutes the liquid crystal display panel and formspixel electrodes, TFTs (thin film transistors) and the like thereon anda counter substrate which constitutes the liquid crystal display paneland forms color filters thereon, a thickness of each substrate isstandardized to 0.5 mm or 0.7 mm, for example. It is difficult to obtainsuch standardized glass substrate from a market. Further, such anextremely thin glass substrate causes drawbacks with respect to amechanical strength, deflection and the like during a manufacturingprocess thus lowering a manufacturing yield rate. As a result, a liquidcrystal display panel is formed using a standardized glass substrateand, thereafter, an outer surface of the liquid crystal display panel ispolished to reduce the thickness of the liquid crystal display panel.

When the thickness of the liquid crystal display panel is reduced, therearises a drawback with respect to a mechanical strength of the liquidcrystal display panel. That is, when a mechanical pressure is applied toa display screen of the liquid crystal display panel, there arises apossibility that the liquid crystal display panel is broken. To preventsuch a drawback, as shown in FIG. 8, in incorporating the liquid crystaldisplay panel in a mobile phone set or the like, a front window(hereinafter, referred to as a face plate) is mounted on a screen sideof the liquid crystal display panel.

To prevent an external force applied to the face plate from beingapplied to the liquid crystal display panel, the face plate is arrangedin a spaced-apart manner from the liquid crystal display panel. However,the constitution shown in FIG. 8 gives rise to a drawback that displayquality is deteriorated as described later. Japanese patent Laid-OpenHei 11-174417 (patent document 1) discloses a technique which isprovided for coping with the drawback attributed to the structure shownin FIG. 8, for example.

SUMMARY OF THE INVENTION

With respect to the related art shown in FIG. 8, there arises a drawbackthat an image appears double. FIG. 8 is a view showing a reflectiveliquid crystal display panel as an example of the liquid crystal displaypanel. In FIG. 8, the liquid crystal display panel is constituted of aTFT substrate 11 on which pixel electrodes, TFTs (thin film transistors)and the like are formed, and a counter substrate 12 on which colorfilters and the like are formed. In FIG. 8, external light L isincident, passes a face plate 30, is reflected on the liquid crystaldisplay panel, passes the face plate 30 again, and enters an eye of aperson. Here, although external light L is refracted on the face plate30, such refraction is ignored in FIG. 8.

A portion of light which is reflected on a screen P1 of the liquidcrystal display panel is reflected on a lower surface Q1 of the faceplate 30, and is incident on and is reflected on a screen P2 of theliquid crystal display panel. When a person observes the light reflectedon the screen P2, there arises a phenomenon that an image appearsdouble. Although the explanation has been made by taking the reflectiveliquid crystal display panel shown in FIG. 8 as an example, the samegoes for a transmissive liquid crystal display panel. That is, in thetransmissive liquid crystal display panel, when light passes the liquidcrystal display panel at the same angle as reflection light on thescreen P1 of the liquid crystal display panel, the light is reflected onthe lower surface Q1 of the face plate 30, and takes the same path inthe same manner as in the case of the reflective liquid crystal displaypanel. Such a phenomenon which makes an image appear double deterioratesan image quality.

To cope with such a drawback, the technique disclosed in patent document1, for example, arranges an adhesive elastic body between the face plateand the liquid crystal display panel. This adhesive elastic body isprovided for protecting the liquid crystal display panel from anexternal force and, at the same time, for suppressing reflection oflight on an interface of the face plate by setting a refractive index ofthe adhesive elastic body to a value close to a refractive index of theface plate. However, with respect to the technique disclosed in patentdocument 1, the uniform lamination of the face plate while eliminatingthe presence of bubbles or the like between the face plate and theelastic adhesive material is an extremely difficult technique from aviewpoint of mass production. Further, in addition to a drawback thatthe selection of a material which makes a refractive index of theelastic adhesive material approximate a refractive index of the faceplate is difficult, the elastic adhesive material requires aconsiderable thickness and hence, the drawback that an image appearsdouble cannot be overcome completely.

To satisfy a demand on design, it is often the case that apicture-frame-shaped light blocking film is formed on the face platewhich is mounted on the liquid crystal display panel. Thepicture-frame-shaped light blocking film is formed such that black inkis applied to the face plate by printing, and printed black ink is driedand solidified by baking the face plate. An additive is used forpreventing the occurrence of pin holes at the time of printing black inkor for leveling a printed surface due to a leveling effect. In adheringthe face plate to the liquid crystal display panel by an adhesivematerial, this additive may adversely influence an adhesive strength ofthe additive.

The present invention has been made to overcome the above-mentioneddrawbacks and it is an object of the present invention to provide aliquid crystal display device which can prevent the generation ofbubbles attributed to an adhesive strength at the time of adhering aface plate to a liquid crystal display panel.

To explain the specific constitutions of the present invention, they areas follows.

(1) The present invention is directed to a liquid crystal display devicewhich includes a liquid crystal display panel constituted of a TFTsubstrate on which pixel electrodes and TFTs which control signals tothe pixel electrodes are arranged in a matrix array, and a countersubstrate on which color filters corresponding to the pixel electrodesare formed, wherein an upper polarizer is adhered to the countersubstrate, a face plate made of glass is adhered to the upper polarizer,the upper polarizer and the face plate are adhered to each other usingan ultraviolet curing resin, a picture-frame-shaped light blocking filmis formed on an inner side of the face plate, the light blocking film isformed by printing black ink, and the black ink contains not more than0.7% and not less than 0.01% of Si.

(2) A liquid crystal display device having the constitution (1) ischaracterized in that the light blocking film contains not more than0.5% and not less than 0.01% of Si.

(3) A liquid crystal display device having the constitution (1) ischaracterized in that the black ink contains carbon black.

(4) A liquid crystal display device having the constitution (1) ischaracterized in that the picture-frame-shaped light blocking film isformed by printing the black ink on the face plate and by drying theblack ink under conditions of not more than 70° C. and not more than 30minutes.

(5) A liquid crystal display device having the constitution (1) ischaracterized in that the picture-frame-shaped light blocking film isformed by printing the black ink on the face plate and by drying theblack ink under conditions of not more than 60° C. and not more than 60minutes.

(6) A liquid crystal display device having the constitution (1) ischaracterized in that the face plate is made of an acrylic resin.

(7) The present invention is also directed to a liquid crystal displaydevice which includes a liquid crystal display panel constituted of aTFT substrate on which pixel electrodes and TFTs which control signalsto the pixel electrodes are arranged in a matrix array, and a countersubstrate on which color filters corresponding to the pixel electrodesare formed, wherein an upper polarizer is adhered to the countersubstrate, a face plate made of glass is adhered to the upper polarizer,and the upper polarizer and the face plate are adhered to each otherusing an ultraviolet curing resin, and a picture-frame-shaped lightblocking film is formed on an inner side of the face plate, the lightblocking film is formed by printing black ink, and the black inkcontains a carbon-hydride-based additive.

(8) A liquid crystal display device having the constitution (7) ischaracterized in that the black ink contains not more than 1.2% and notless than 0.1% of the carbon-hydride-based additive.

(9) A liquid crystal display device having the constitution (7) ischaracterized in that a Si content of the black ink is less than 0.01%.

(10) A liquid crystal display device having the constitution (7) ischaracterized in that the black ink contains carbon black.

(11) A liquid crystal display device having the constitution (7) ischaracterized in that the face plate is made of an acrylic resin.

According to the present invention, in the liquid crystal display devicewhich forms the light blocking film on the periphery of the face plate,for enhancing design property, the light blocking film is formed byprinting the black ink on the periphery of the face plate. Here, bysetting a quantity of Si contained in the black ink to not more than0.7% and not less than 0.01%, it is possible to prevent the generationof bubbles between the face plate and the liquid crystal display panelwhen the face plate is adhered to the liquid crystal display panel. Atthe same time, the occurrence of pin holes at the time of printing canbe prevented, and a printed surface can be leveled due to a levelingeffect.

Further, according to another aspect of the present invention, with theuse of the carbon-hydride-based additive as the additive of the blackink to be printed on the periphery of the face plate, it is possible toprevent the generation of bubbles between the face plate and the liquidcrystal display panel when the face plate is adhered to the liquidcrystal display panel. At the same time, the occurrence of pin holes atthe time of printing can be prevented, and a printed surface can beleveled due to a leveling effect.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of a liquid crystal displaydevice to which the present invention is applied;

FIG. 2 is a cross-sectional view taken along a line A-A in FIG. 1;

FIG. 3A and FIG. 3B are views showing a state in which a face plate ismounted on the liquid crystal display panel;

FIG. 4A and FIG. 4B are views showing a state in which bubbles aregenerated between the face plate and the liquid crystal display panel;

FIG. 5 is a schematic view showing essential manufacturing stepsrelating to the present invention;

FIG. 6 is a flowchart of the manufacturing steps relating to the presentinvention;

FIG. 7 is a graph showing the relationship between a drying condition ofthe face plate and a quantity of Si in ink on the face plate; and

FIG. 8 is a view showing the relationship between a face plate and aliquid crystal display panel of a related art.

DETAILED DESCRIPTION OF THE INVENTION Embodiment 1

The detailed content of the present invention is explained in accordancewith embodiments.

FIG. 1 is an exploded perspective view showing an embodiment 1 of thepresent invention. FIG. 2 is an exploded cross-sectional view takenalong a line A-A in FIG. 1. In FIG. 1, a liquid crystal display panel isconstituted of a TFT substrate 11 and a counter substrate 12. Pixelelectrodes are formed on the TFT substrate 11 in a matrix array, andeach pixel electrode is provided with a TFT (Thin Film Transistor) forswitching a signal. The counter substrate 12 on which color filters areformed is arranged to face the TFT substrate 11 in an opposed manner.

In manufacturing the TFT substrate 11 and the counter substrate 12respectively, a glass substrate which is used for forming the TFTsubstrate 11 and the counter substrate 12 has a thickness of 0.5 mm.After completing a liquid crystal display panel by sealing liquidcrystal in a space defined between the TFT substrate 11 and the countersubstrate 12, an outer side of the liquid crystal display panel ispolished so as to reduce a thickness of the whole liquid crystal displaypanel. In this embodiment, a thickness of the liquid crystal displaypanel after polishing is set to an approximately 0.6 mm. That is, thethicknesses of respective glass substrates are reduced by polishing by0.2 mm.

The TFT substrate 11 is formed larger than the counter substrate 12, anda drive IC 13 and a flexible printed circuit board 15 are mounted on aportion of the TFT substrate 11 which is formed as a single plate. Theliquid crystal display panel is housed in a resin mold 16 so that theliquid crystal display panel is mechanically protected. The liquidcrystal display panel exhibits a high mechanical strength at a portionthereof where the TFT substrate 11 and the counter substrate 12 overlapwith each other. However, the liquid crystal display panel exhibits alow mechanical strength at a portion thereof which is constituted of asingle plate, that is, of only the TFT substrate 11. To prevent animpact from being applied to such a portion which exhibits a lowmechanical strength, the liquid crystal display panel has the moldstructure.

A backlight is arranged below the mold 16. In FIG. 1, only a light guideplate 17 of the backlight is shown. That is, although various opticalsheets are arranged between the liquid crystal display panel and thelight guide plate 17, these optical sheets are omitted from FIG. 1. Theflexible printed circuit board 15 is routed to a back side of the mold16 and is arranged below the backlight. On the flexible printed circuitboard 15, an LED 18 (Light Emitting Diode) which constitutes a lightsource of the backlight is mounted. The LED 18 is arranged on a sidesurface of the light guide plate 17. On the flexible printed circuitboard 15, not only the LED 18 and a power source of the LED 18 but alsoa power source for driving the liquid crystal display panel and lineswhich form scanning lines and data signal lines and the like arearranged.

In FIG. 1, an upper polarizer 14 is mounted on an upper surface of theliquid crystal display panel. A face plate 30 is mounted on the upperpolarizer 14. The face plate 30 is made of an acrylic resin, and athickness of the face plate 30 is set to 1.8 mm. The thickness of theface plate 30 is set larger than a thickness of the liquid crystaldisplay panel and cracks hardly occur in the acrylic resin and hence,the face plate 30 possesses a sufficient mechanical strength forprotecting the liquid crystal display panel. The face plate 30 isadhered to the liquid crystal display panel, to be more specific, to theupper polarizer 14 using an acrylic adhesive material 31.

As other material which can be used for forming the face plate 30,poly-carbonate, glass or the like is named. In using glass as a materialof the face plate 30, it is preferable to use reinforced glass. Further,it is necessary to properly chamfer glass-made face plate 30 forpreventing the occurrence of cracks in the face plate 30.

As shown in FIG. 1, a black picture frame 50 is formed on a periphery ofthe face plate 30. The black picture frame 50 is provided for enhancingdesign property of the liquid crystal display device. The picture frame50 is formed by printing a black light blocking material on the faceplate 30. For example, when Si or the like leaks from the light blockingmaterial used for forming the picture frame 50, there exists apossibility that leaked Si may adversely influence adhesiveness betweenthe adhesive material 31 and the face plate 30 so that bubbles may begenerated in the adhesive material 31. The present invention issubstantially characterized by the constitution which can prevent thegeneration of bubbles between the face plate 30 and the liquid crystaldisplay panel by suppressing leaking of Si from the picture frame 50.

FIG. 2 is an exploded cross-sectional view taken along a line A-A inFIG. 1. In an actual constitution, the liquid crystal display panel andthe backlight are housed in the mold 16. The face plate 30 is adhered tothe liquid crystal display panel. In FIG. 2, a gap of few microns ispresent between the TFT substrate 11 and the counter substrate 12, andliquid crystal 100 is sandwiched between the TFT substrate 11 and thecounter substrate 12. A sealing material 19 is formed on peripheries ofthe TFT substrate 11 and the counter substrate 12 so as to seal theliquid crystal 100 in a space defined by the TFT substrate 11, thecounter substrate 12 and the sealing material 19.

On the TFT substrate 11, in addition to the pixel electrodes and theTFTs, scanning lines, data signal lines and the like are arranged. Theselines extend to the outside while penetrating the sealing material 19and are connected to the drive IC 13 or the flexible printed circuitboard 15. The flexible printed circuit board 15 extends to a back sideof the backlight. The LED 18 mounted on the flexible printed circuitboard 15 is arranged on a side surface of the light guide plate 17 andconstitutes a light source of the backlight. A plurality of LEDs 18 isarranged in the direction perpendicular to a paper plane of FIG. 2.

In FIG. 2, the light guide plate 17 plays a role of directing lightwhich is emitted from the LEDs 18 arranged on a side surface of thelight guide plate 17 in the direction toward the liquid crystal displaypanel side. A reflection sheet 25 directs light which is directeddownwardly from the light guide plate 17 in the direction toward theliquid crystal display panel side. A lower diffusion sheet 21 is mountedon the light guide plate 17. Although the plurality of LEDs 18 ismounted on the side surface of the light guide plate 17, the LEDs 18 arearranged at intervals and hence, light which is directed upwardly fromthe light guide plate 17 becomes non-uniform. That is, areas surroundingpositions where the LEDs 18 are arranged exhibit more brightness. Thelower diffusion sheet 21 plays a role of making light which is directedin the upward direction from the light guide plate 17 uniform.

A lower prism sheet 22 is mounted on the lower diffusion sheet 21. Alarge number of prisms which extend in the lateral direction of thescreen are mounted on the lower prism sheet 22 at fixed intervals, forexample, at intervals of approximately 50 μm. Out of the light which isradiated from the light guide plate 17, the prisms converge light whichis liable to spread in the longitudinal direction of the screen in thelongitudinal direction of the screen of the liquid crystal displaypanel. An upper prism sheet 23 is mounted on the lower prism sheet 22.On the upper prism sheet 23, a large number of prisms which extend inthe direction orthogonal to the lower prism sheet 22, for example, inthe longitudinal direction of the screen are formed at fixed intervals,that is, at intervals of approximately 50 μm. Due to such constitution,out of the light which is radiated from the light guide plate 17, theprisms converge light which is liable to spread in the lateral directionof the screen in the direction normal to a surface of the liquid crystaldisplay panel. As described above, with the use of the lower prism sheet22 and the upper prism sheet 23, light which is liable to spread in thelongitudinal and lateral directions of the screen can be converged inthe normal direction of the screen. That is, with the use of the lowerprism sheet 22 and the upper prism sheet 23, front-face brightness ofthe screen can be increased.

An upper diffusion sheet 24 is mounted on the upper prism sheet 23. Aplurality of prisms which extends in the predetermined direction isformed on the prism sheet at intervals of 50 μm, for example. That is,bright and dark stripes are formed at intervals of 50 μm. On the otherhand, on the liquid crystal display panel, the scanning lines are formedin the lateral direction of the screen at fixed intervals, and the datasignal lines are formed in the longitudinal direction of the screen atfixed intervals. Accordingly, interference is generated between thescanning lines and the lower prism sheet 22 or between the data signallines and the upper prism sheet 23 thus generating moire fringes. Theupper diffusion sheet 24 plays a role of reducing the moire fringes by adiffusion action.

Light radiated from the upper diffusion sheet 24 is incident on thelower polarizer 20 which is adhered to the liquid crystal display paneland is polarized. The polarized light has transmissivity thereofcontrolled by liquid crystal in the inside of the liquid crystal displaypanel for every pixel thus forming an image. The light which is radiatedfrom the liquid crystal display panel is polarized again by the upperpolarizer 14, and is visually recognized by eyes of a person. The faceplate 30 is mounted on the upper polarizer 14. The face plate 30 of thepresent invention is made of an acrylic resin. The face plate 30 isadhered to the upper polarizer 14 using the adhesive material 31.

FIG. 3A and FIG. 3B show a state after the face plate 30 is adhered tothe upper polarizer 14. FIG. 3A and FIG. 3B show only the liquid crystaldisplay panel and the face plate 30. FIG. 3A is a plan view, and FIG. 3Bis a cross-sectional view taken along a line A-A in FIG. 3A. In FIG. 3A,a black picture frame 50 is formed on the periphery of the face plate30. A display region 40 is formed inside the picture frame 50. Thepicture frame 50 is provided for enhancing design property of the liquidcrystal display panel. In FIG. 3A, a terminal portion 111 of the TFTsubstrate 11 is arranged on a left side. Although terminals forsupplying power source and signals to the liquid crystal display panel,the drive IC for driving the liquid crystal display panel and the likeare mounted on the terminal portion 111, these parts are omitted fromFIG. 3.

In FIG. 3B, the lower polarizer 20 is adhered to a lower side of the TFTsubstrate 11, and the upper polarizer 14 is adhered to an upper side ofthe counter substrate 12. The face plate 30 is mounted on the upperpolarizer 14 by way of the adhesive material 31. A plate thickness ofthe upper polarizer 14 or the lower polarizer 20 is set to 0.13 mm, anda thickness of the face plate 30 is set to 1.8 mm. Compared to a factthat a total thickness of the liquid crystal display panel which isformed by combining the TFT substrate 11 and the counter substrate 12 isset to 0.6 mm, the face plate 30 has a thickness considerably largerthan the total thickness of the liquid crystal display panel. Further,cracks hardly occur in the acrylic resin compared to glass and hence,the face plate 30 can acquire a mechanical strength considerably largerthan a mechanical strength of the liquid crystal display panel thusexhibiting a sufficient mechanical protection effect.

In this embodiment, a size of the face plate 30 is set substantiallyequal to a size of the counter substrate 12. The size of the face plate30 is not limited to the above-mentioned size, and may be set larger orsmaller than the size of the counter substrate 12 by taking easiness ofadhesion between the face plate 30 and the liquid crystal display panelinto consideration.

The picture frame 50 formed on the periphery of the face plate 30 ispreliminarily applied to the face plate 30 by printing and is solidifiedby drying and, thereafter, the face plate 30 and the liquid crystaldisplay panel are adhered to each other using the adhesive material 31.As the adhesive material 31 used for adhering the face plate 30, anultraviolet curing resin which is in a liquid form originally is used.By adopting the ultraviolet curing resin which is in a liquid formoriginally as the adhesive material 31, the face plate 30 can beuniformly adhered to the liquid crystal display panel. That is, afterapplying the adhesive material 31, the liquid crystal display panel andthe face plate 30 are adhered to each other under a reduced-pressureatmosphere. By adhering the liquid crystal display panel and the faceplate 30 under a reduced-pressure atmosphere, it is possible to preventthe generation of bubbles 32.

After performing such an adhesion, by radiating ultraviolet rays (UV) tothe adhesive material 31 which is in a liquid form originally, theadhesive material 31 is cured thus fixing the face plate 30 to theliquid crystal display panel. Due to such processing, the face plate 30can be uniformly adhered to the liquid crystal display panel. As theadhesive material 31 which is in a liquid form originally, an acrylicresin which contains 27% to 30% of acrylic oligomer, UV-reactivemonomer, an additive for the photo-polymerization and the like may beused. A thickness of a cured adhesive material 31 is set toapproximately 50 μm.

The light blocking film which constitutes the picture frame 50 is formedby applying black ink to an inner side of the face plate 30 by printing.The black ink is, for example, constituted of following components. Thatis, the black ink contains 26% to 38% of a mixed resin made ofpoly-vinyl chloride acetate copolymer and a urethane resin, 3% to 7% ofpigment (carbon black), other solvents and the like.

In printing the black ink to the face plate 30, there may be a case thatpin holes are formed in the light blocking film. Further, although someirregularities may occur on a printed surface after applying the blackink to the face plate 30 by printing, the irregularities are leveled dueto the flow of the printed surface. This phenomenon is referred to as aleveling effect. The addition of Si to the black ink is effective inpreventing the occurrence of the pin holes in the printed surface and inenhancing the leveling effect of the printed surface.

After applying the black ink to the face plate 30, the black ink isfixed to the face plate 30 by drying the face plate 30. When an additionquantity of Si is large, Si is diffused into the outside of the lightblocking film, for example, the periphery of the display region 40. Whena large quantity of Si is present between the face plate 30 and theadhesive material 31, an adhesive strength between the face plate 30 andthe adhesive material 31 becomes weak and hence, the bubbles 32 aregenerated.

FIG. 4A and FIG. 4B show a mechanism how the bubbles 32 are generated.FIG. 4A is a plan view, and FIG. 4B is a cross-sectional view takenalong a line A-A in FIG. 4A. In FIG. 4A, a dotted line drawn in thedisplay region 40 indicates a region having a possibility that Sileaking from the light blocking film which constitutes the picture frame50 is present. This region falls within a range which is inwardly awayfrom an inner side of the picture frame 50 by “d”, and a width of “d” is2 mm. This region constitutes an Si-diffusion area 41. A large quantityof bubbles 32 is generated in the Si-diffusion area 41.

FIG. 4B is a cross-sectional view taken along a line A-A in FIG. 4A. Theconstitution shown in FIG. 4B is substantially equal to the constitutionshown in FIG. 3B except for that the bubbles 32 are shown in FIG. 4B.FIG. 4B shows that the bubbles 32 are generated inside the picture frame50 and between the face plate 30 and the adhesive material 31. Althoughthe bubbles 32 are also generated below the picture frame 50, thebubbles 32 generated below the picture frame 50 are covered with theblack picture frame 50 and hence, such bubbles 32 are not visuallyrecognized whereby there is no possibility that such bubbles 32 become adefect of the display device. Accordingly, the elimination of thebubbles 32 generated in the periphery of the display region 40 isimportant.

When an element of a portion where the bubbles 32 are present isidentified, a large quantity of Si is detected. Si deteriorates anadhesive strength between the adhesive material 31 and the face plate 30and generates the bubbles 32. However, the addition of Si into the blackink for forming the picture frame 50 is necessary for enhancing thereduction of pin holes and a leveling effect.

The presence of Si in the display region 40 is attributed to thedispersion of Si in the display region 40 when black ink is printed andsolidified by drying. Further, provability of the generation of thebubbles 32 differs depending on a quantity of Si present in black ink.That is, when a quantity of Si is equal to or below a fixed value, thegeneration of the bubbles 32 can be suppressed. A quantity of Si in thedisplay region 40 can be controlled by a quantity of Si added to blackink.

Accordingly, an addition quantity of Si in black ink is determined bytaking the occurrence of pin holes during printing, the leveling effectand a rate of generation of the bubbles 32 after the face plate 30 isadhered to the liquid crystal display panel into consideration.According to an experiment, when the above-mentioned black ink is used,by setting a quantity of Si contained in black ink to not more than 0.7%and not less than 0.01% of a content of the light blocking film whichconstitutes the picture frame 50, it is possible to suppress thegeneration of the bubbles 32 while ensuring the prevention of theoccurrence of pin holes and the leveling effect. That is, by suppressinga quantity of Si to a value which falls within such a range, a defectattributed to the occurrence of pin holes and a defect relating to theleveling effect can be suppressed to 0.1% or less. Further, thegeneration of the bubbles 32 can be also suppressed to 1% or less.

Further, by setting a quantity of Si to not more than 0.5% of thecontent of the light blocking film which constitutes the picture frame50, the generation of the bubbles 32 can be further suppressed thusreducing a rate of generation of a defect attributed to the bubbles 32to 0.5% or less. The generation of the bubbles 32 described above can bealso changed depending on a drying condition of black ink after blackink is applied to the face plate 30 by coating. That is, the higher adrying temperature or the longer a drying time, the larger a chance thatSi is diffused to the outside of the picture frame 50 becomes. Theabove-mentioned results are values which are acquired when the faceplate 30 is dried at a temperature of 70° C. for 60 minutes afterapplying black ink to the face plate 30 by coating. Accordingly, thegeneration of the bubbles 32 can be further reduced by lowering thedrying temperature or shortening the drying time.

FIG. 5 is a schematic view showing steps of forming a hybrid liquidcrystal display panel which is formed by combining the liquid crystaldisplay panel and the face plate 30 shown in FIG. 3. In FIG. 5, FIGS. 5(a) and (b) show steps of forming the face plate 30, FIG. 5( c) shows astep of forming the liquid crystal display panel, and FIG. 5( d) shows astate in which the liquid crystal display panel and the face plate 30are laminated to each other. As shown in FIG. 5, a plurality of faceplates 30 is formed in a mother face plate 130. Further, the liquidcrystal display panel is also the combination of a mother TFT substrate110 in which a plurality of TFT substrates 11 are formed and a mothercounter substrate 120 in which a plurality of counter substrates 12 areformed. FIG. 5 shows an example in which four face plates 30 or fourliquid crystal display panels are formed from the mother substrate.

In FIG. 5( a), black ink is formed on the mother face plate 130 byprinting for forming the picture frame 50. Printing conditions and amaterial of black ink are determined such that pin holes do not occur inthe printed black ink or a printed surface becomes flat due to aleveling effect. After printing, black ink is solidified by drying themother face plate 130 under specific conditions.

Thereafter, as shown in FIG. 5( b), a UV curing resin is applied to thedisplay region 40 of the face plate 30 and the picture frame 50 byprinting. The UV curing resin is in a liquid form at the time ofprinting. As a material of the UV curing resin, the material which isexplained previously can be used.

On the other hand, as shown in FIG. 5( c), the liquid crystal displaypanel is formed separately from the face plate 30. That is, the TFTsubstrates 11 amounting to four pieces of liquid crystal display panelsare formed in the mother TFT substrate 110. Further, the countersubstrates 12 amounting to four liquid crystal display panels are formedin the mother counter substrate 120. In FIG. 5( c), portions indicatedby a dotted line are sealing portions 60 for sealing the TFT substrates11 and the counter substrates 12. Liquid crystal is sealed inside eachsealing portion 60. Liquid crystal may be filled by either a droppingmethod or a suction method. In this manner, four pieces of liquidcrystal display panels are formed in the mother substrate.

The mother face plate 130 formed as shown in FIG. 5( b) is inverted, andis adhered to the mother counter substrate 120 of the mother liquidcrystal display panel formed as shown in FIG. 5( c). This adhesion isperformed by a UV adhesive material 31 formed on the mother face plate130. This adhering step is performed in a pressure-reduced atmospherefor preventing entanglement of air into the adhering portion.Thereafter, ultraviolet rays are radiated to a portion of the UVadhesive material 31 for temporarily fixing the mother face plate 130 tothe mother counter substrate 120, and the inspection of bubbles 32 orthe like is performed.

FIG. 6 is a flowchart showing a process flow consisting of steps offorming a hybrid liquid crystal display panel which is formed bycombining the liquid crystal display panel and the face plate 30 shownin FIG. 3. Hereinafter, the combination of the liquid crystal displaypanel and the face plate 30 is referred to as the hybrid liquid crystaldisplay panel. The steps of this process flow are applied, as shown inFIG. 5, to the mother liquid crystal display panel or the mother faceplate 130. Then, after finishing steps shown in FIG. 6, the individualhybrid liquid crystal display panels are separated from the mothersubstrate. Hereinafter, in the explanation of the process flow shown inFIG. 6, there may be a case that the face plate 30 and the liquidcrystal display panel refer to the mother face plate 130 and the motherliquid crystal display panel.

In FIG. 6, the center flow is the process flow of the face plate 30.FIG. 6, step 601 implies a DUV(Deep UV) step in which deep ultravioletrays are radiated to the face plate 30. By radiating deep ultravioletrays to the face plate 30, dusts or the like adhered to the face plate30 can be easily removed. After cleaning the face plate 30 in the DUVstep, first of all, black ink which becomes the picture frame 50 of theface plate 30 is applied by printing (step 602: light blocking portionprinting step). In this light blocking printing step, a material ofblack ink or printing conditions are determined such that pin holes donot occur or a printed surface becomes flat due to a leveling effect.

The face plate 30 on which the picture frame 50 is printed using blackink is baked for drying. At the time of performing such baking, theremay arise a drawback that Si added to black ink precipitates from theprinted picture frame 50 and is diffused in the display region 40arranged inside the picture frame 50. When a diffusion quantity of Si islarge, Si adversely influences the adhesion between the adhesivematerial 31 and the face plate 30.

FIG. 7 is a graph which compares a quantity of Si present in the Sidiffusion region 41 of the face plate 30 which is changed depending ondrying conditions of the face plate 30. In FIG. 7, a drying temperature(° C.) at which the face plate 30 is dried after printing black ink onthe face plate 30 is taken on an axis of abscissas. The count number ofSi (K amu.bin) counted by a mass spectrometric analysis in the Sidiffusion region 41 shown in FIG. 4 is taken on an axis of ordinates.The evaluation in FIG. 7 is made with respect to a case in which dryingtime is set to 30 minutes and a case in which drying time is set to 60minutes.

In FIG. 7, the higher the drying temperature, the larger the countnumber of Si in the Si diffusion region 41 becomes. Further, when thedrying temperatures are the same in both cases, the longer the dryingtime, the larger the count number of Si becomes. That is, when theprinted black ink is dried and solidified, Si added to black ink isprecipitated and separated from black ink, and in this precipitation andseparation of Si, the higher the drying temperature or the longer thedrying time, a precipitation or separation quantity of Si is increased.Further, the higher the drying temperature or the longer the dryingtime, a speed at which precipitated or separated Si moves on the faceplate 30 or a moving amount of such Si is also increased.

Si is added to black ink for ensuring the prevention of occurrence ofpin holes and a leveling effect at the time of printing. When it isnecessary to ensure a fixed amount of Si to be added to black ink inview of the relationship between pin holes and leveling at the time ofprinting, it is necessary to shorten the drying time or lower the dryingtemperature after printing. FIG. 7 is the graph which shows therelationship among the drying temperature, the drying time and the countquantity of Si in the Si diffusion region 41 shown in FIG. 4 when thequantity of Si in the light blocking film for forming the picture frame50 after drying and solidifying is 0.7%.

In FIG. 7, under the condition that the drying temperature is set to 70°C., when the drying time is 30 minutes, Si count quantity becomes 150Kamu.bin. In this case, the occurrence ratio of bubbles 32 correspondingto the Si count quantity is suppressed to 1% or less. On the other hand,under the condition that the drying temperature is set to 60° C., evenwhen the drying time is set to 60 minutes, the Si count quantity is 100K amu.bin. In this case, the occurrence ratio of bubbles 32corresponding to the Si count quantity also can be suppressed to 1% orless. Further, by setting the drying temperature to 60° C. and thedrying time to 30 minutes, possibility of generation of bubbles 32 canbe further reduced. On the other hand, even when the Si quantity isdecreased, provided that the occurrence of pin holes can be suppressedor the leveling effect can be ensured, it is possible to elevate thedrying temperature of the face plate 30 or extend the drying time.

Returning to FIG. 6, black ink is printed on the face plate 30, and thepicture frame 50 is formed by drying black ink. Thereafter, the adhesivematerial 31 for adhering the face plate 30 and the liquid crystaldisplay panel is applied by printing (step 603). The adhesive material31 is made of a UV curing resin. The adhesive material 31 is printedsuch that the adhesive material 31 covers the display region 40 of theface plate 30 and the picture frame 50.

The lamination of the liquid crystal display panel and the face plate 30is performed under a reduced-pressure atmosphere such that the liquidcrystal display panel 610 and the face plate 30 are adhered to eachother by pushing (step 604). Since the adhesion is performed in thereduced-pressure atmosphere, there is no possibility that air isentangled between the face plate 30 and the liquid crystal display panelthus preventing the generation of bubbles 32 attributed to theentanglement of air. However, when Si is present in the face plate 30,the adhesion between the face plate 30 and the adhesive material 31 isprevented, and there may be a case that air intrudes into such a portionthus generating bubbles 32. Accordingly, it is necessary to remove apossibility that Si is present in the face plate 30 by taking theabove-mentioned means.

After adhering the face plate 30 and the liquid crystal display panel toeach other, ultraviolet rays are radiated to a portion of the adhesivematerial 31, to be more specific, only corner portions of the face plate30 thus temporarily fixing the face plate 30 and the liquid crystaldisplay panel to each other (step 605). In a temporarily fixed state,the inspection of a hybrid liquid crystal display panel which is formedby adhering the face plate 30 and the liquid crystal display panel isperformed (step 606). Inspection items are defects of the display region40 and the like. At the time of performing such inspection, the presenceor the non-presence of the bubbles 32 in the display region 40 is alsoinspected.

When the hybrid liquid crystal display panel passes this inspection,ultraviolet rays are radiated to the whole liquid crystal display panelthus completely adhering the face plate 30 and the liquid crystaldisplay panel to each other (step 607). Ultraviolet rays are radiatedfrom a face plate 30 side. In this case, the picture frame 50 is formedin the periphery of the face plate 30 and hence, ultraviolet rays do notpass below the picture frame 50 whereby the adhesive material 31 belowthe picture frame 50 is not solidified. To solidify the adhesivematerial 31 below the picture frame 50 also, after radiating ultravioletrays to the whole surface of the liquid crystal display panel, thehybrid liquid crystal display panel is heated thus also solidifying theadhesive material 31 below the picture frame 50 of the face plate 30thus enhancing reliability of adhesion (step 608).

In FIG. 6, when a defect occurs in the hybrid liquid crystal displaypanel in the inspection step, the hybrid liquid crystal display panel istransferred to a reproduction step (step 609). In the reproduction step,the face plate 30 and the liquid crystal display panel are separatedfrom each other. The reason that ultraviolet rays are radiated only tothe portion of the adhesive material 31 so as to temporarily fix theface plate 30 and the liquid crystal display panel to each other beforethe inspection is that the liquid crystal display panel and the faceplate 30 can be separated easily in the reproduction step. After theface plate 30 and the liquid crystal display panel are separated fromeach other, the face plate 30 and the liquid crystal display panel areindividually cleaned and are reproduced.

As described above, according to this embodiment, by defining thequantity of Si in the light blocking film which constitutes the pictureframe 50 within the specified range, it is possible to prevent thegeneration of bubbles 32 attributed to lowering of the adhesive strengthbetween the face plate 30 and the adhesive material 31 when the faceplate 30 and the liquid crystal display panel are adhered to each other.Further, this embodiment can prevent the occurrence of pin holes whenblack ink is printed, and can make the printed surface flat by ensuringthe leveling effect at the time of printing.

Embodiment 2

The picture frame 50 of the face plate 30 in the embodiment 1 is formedby printing black ink to which Si is added. Si is used for preventingthe occurrence of pin holes and for making the printed surface flat byleveling at the time of printing black ink. On the other hand, with theuse of Si, an adhesive strength of the adhesive material 31 becomesunstable in the periphery of the display region 40 of the face plate 30,and this unstable adhesive strength becomes a cause of the generation ofbubbles 32.

In this embodiment, a carbon-hydride-based additive is used as theadditive in place of Si. With the use of the carbon-hydride-basedadditive, at the time of printing black ink on the face plate 30, it ispossible to acquire both of the prevention of occurrence of pin holesand the leveling effect. A material of black ink used in this embodimentis substantially equal to the material of black ink explained inconjunction with the embodiment 1. That is, the black ink contains 26%to 38% of a mixed resin made of poly-vinyl chloride acetate copolymerand a urethane resin, 3% to 7% of pigment (carbon black), other solventsand the like. By adding 0.1% to 1.2% of carbon-hydride-based additive tosuch black ink, it is possible to prevent the occurrence of pin holes atthe time of printing black ink and to acquire the leveling effect of theprinted surface.

Such black ink is applied to the face plate 30 by printing, and thepicture frame 50 is formed by drying the face plate 30. Thereafter, theadhesive material 31 is formed by printing in the same manner as theembodiment 1. Then, the face plate 30 and the liquid crystal displaypanel are adhered to each other so as to form a hybrid liquid crystaldisplay panel. In this embodiment, a quantity of Si in black ink is lessthan 0.01%. Since Si is not substantially present in black ink andhence, there arises no drawback with respect to the adhesion between theface plate 30 and the adhesive material 31. That is, in the region wherea large quantity of bubbles 32 is generated in FIG. 4, similar bubbles32 are not observed.

In this manner, with the use of black ink of this embodiment, it ispossible to substantially eliminate the generation of the bubbles 32attributed to defective adhesion between the adhesive material 31 andthe face plate 30 in printing black ink. Further, this embodiment canprevent the occurrence of pin holes at the time of printing black inkand, at the same time, can make the printed surface flat by ensuring theproper leveling effect.

1-6. (canceled)
 7. A liquid crystal display device which includes aliquid crystal display panel constituted of a TFT substrate on whichpixel electrodes and TFTs which control signals to the pixel electrodesare arranged in a matrix array, and a counter substrate on which colorfilters corresponding to the pixel electrodes are formed, wherein anupper polarizer is adhered to the counter substrate, a face plate madeof glass is adhered to the upper polarizer, and the upper polarizer andthe face plate are adhered to each other using an ultraviolet curingresin, and a picture-frame-shaped light blocking film is formed on aninner side of the face plate, the light blocking film is formed byprinting black ink, and the black ink contains a carbon-hydride-basedadditive.
 8. A liquid crystal display device according to claim 7,wherein the black ink contains not more than 1.2% and not less than 0.1%of the carbon-hydride-based additive.
 9. A liquid crystal display deviceaccording to claim 7, wherein a Si content of the black ink is less than0.01%.
 10. A liquid crystal display device according to claim 7, whereinthe black ink contains carbon black.
 11. A liquid crystal display deviceaccording to claim 7, wherein the face plate is made of an acrylicresin.